<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>day01</title>
    <style type="text/css">
        *{margin: 0px; padding: 0px}
        .main{width:100px; height: 100px; background: #ffff00; transition-timing-function: linear; transition-duration: 5000ms;
        }
        .main:hover{width: 300px}
        .absolute{width: 300px; height: 300px; position: relative; border: 1px solid}
    </style>
</head>
<body>
    <div class="main"></div>
    <div class="absolute">
        <div>111</div>
    </div>
</body>
</html>